1,equals
@test
public void test_equal(){
string a="1";
int b=1;
boolean result=a.equals(b);
system.out.println(result);
}
我以為會報錯的,因為類型不同啊,一個是字元串,一個是整型. 結果沒有報錯.
原因:equals 比較時自動把基本類型轉化為包裝類型了
運作結果是:
false
應該改為:
boolean result=a.equals(string.valueof(b));
2,包裝類型
public void test_equal2(){
long a=229l;
long b=229l;
system.out.println((a==b));
運作結果:false
long a=29l;
long b=29l;
運作結果為:true
system.out.println((a.intvalue()==b.intvalue()));
3,把json字元串反序列化為對象
當json字元串是空時竟然不報錯,示例如下:
objectmapper mapper = new objectmapper();
student2 student;
try {
student = mapper.readvalue("{}", student2.class);
system.out.println(student.getclassroom());
system.out.println(student.getschoolnumber());
} catch (exception e) {
e.printstacktrace();
}
運作結果:
但是,如果json字元串中包含的屬性,對象中沒有則報錯
student = mapper.readvalue("{\"username2323\":\"whuang\"}", student2.class);
student2類中沒有屬性username2323
報錯資訊:
org.codehaus.jackson.map.exc.unrecognizedpropertyexception: unrecognized field "username2323" (class tv_mobile.student2), not marked as ignorable
at [source: java.io.stringreader@7bb613c0; line: 1, column: 18] (through reference chain: tv_mobile.student2["username2323"])
at org.codehaus.jackson.map.exc.unrecognizedpropertyexception.from(unrecognizedpropertyexception.java:53)
http://blog.csdn.net/hw1287789687/article/details/45916001
作者:黃威